The project aims are to advance, through in vitro studies, our understanding of the trophic interactions between neural retina and optic tectum, as well as the mechanisms accounting for selective neuritic growth during development of the visual system. Specifically, we intend to continue our investigation of: 1) identity and cytochemical properties of cultured neural retina cells; 2) effects of optic lobe extracts on those cells; 3) properties of the molecules responsible for those effects, and 4) regulation of neuritic growth and guidance by a newly identified "Neurite Promoting Factor".